South Korea and Japan condemned North Korea's deployment of troops and transfer of missiles to support Russia in its war against Ukraine during a U.N. General Assembly forum Tuesday,

SEOUL, Sept. 2 (UPI) -- South Korea and Japan condemned North Korea's deployment of troops and transfer of missiles to support Russia in its war against Ukraine during a U.N. General Assembly forum Tuesday, with Seoul calling for an immediate end to the military cooperation.

South Korea's Ambassador to the United Nations Jihoon Cha made the comments during a debate on the situation in Ukraine, saying Seoul remains "seriously concerned" about continuing military ties between Moscow and Pyongyang.

"Despite repeated calls at each session, this cooperation continues unabated, including arms and ballistic missile transfers, troop deployments and other forms of military support," Cha said. "Such cooperation continues to prolong the war while posing a serious threat to international peace and security."

Cha added that the North's transfers of arms and ballistic missiles violate Security Council resolutions and run counter to the spirit and principles of the U.N. Charter.

"The Republic of Korea therefore urges Russia and the DPRK to immediately cease their unlawful military cooperation," Cha said, using the official acronym for North Korea.

Japanese Ambassador to the United Nations Kazuyuki Yamazaki also spoke out against Pyongyang-Moscow ties, saying Tokyo is "deeply concerned by the continued engagement of North Korea, including the deployment of soldiers in combat against Ukraine."

"Such unlawful military cooperation between Russia and the DPRK is undermining peace and security in Europe, in the Pacific and beyond," Yamazaki said.

"Any action that directly or indirectly supports Russia's aggression is itself a violation of international law, and all states complicit in such aggression must be held accountable," he added.

The criticism comes as Washington and Seoul have sought to revive diplomacy with Pyongyang, with U.S. President Donald Trump saying last month that he expects to meet North Korean leader Kim Jong Un this year.

North Korea has sent munitions, missiles and roughly 15,000 troops to support Russian forces in the Kursk region, according to South Korea's National Intelligence Service, which estimates that about 2,000 of the deployed troops have been killed.

Last month, Ukrainian President Volodymyr Zelensky said Pyongyang was preparing to deploy an additional 30,000 to 50,000 personnel to Russia and had supplied Moscow with additional ballistic missiles. He warned that the battlefield experience North Korea was gaining in Russia posed a mounting threat to countries in the Asia-Pacific region and called for closer cooperation between Seoul and Kyiv.

Deputy Head of Ukrainian Defense Intelligence Maj. Gen. Vadym Skibitskiy later told CNN that a new wave of North Korean troops in Russia had grown to some 8,500 personnel, including 400 drone operators, many with experience from previous deployments.

Kim Yo Jong, the powerful sister of North Korean leader Kim Jong Un, called reports of additional troop deployments an "ungrounded farce of Kiev."

In a statement carried by the state-run Korean Central News Agency, Kim claimed that the United States and its Western allies were "entirely responsible for the start of the Ukrainian crisis and its prolongation."

"We fully support the righteous action of the Russian government and people to defend the national sovereignty, security interests and territorial integrity," she added.

The United States did not mention North Korea in its remarks at the U.N. session.

U.S. Ambassador Dan Negrea, an alternate representative to the U.N. General Assembly, called for "an immediate ceasefire and good faith negotiations to return peace and stability to both countries."

"Russia and Ukraine must return to the negotiating table as it is clear that no military solution exists for this war," Negrea said.